This chapter shows you how to begin using your Linux
system. It shows you how to boot your system, log in, issue
commands, log out, and shut down your system. It also explains
how to use the
man command, which provides
help on using other commands. The chapter describes how Linux
organizes data as filesystems, directories, and files and how
you can work with removable media, such as diskettes. It
describes how to query the status of your system. And, finally,
it explains how to use
pico, a simple text
editor.
This section introduces you to the cycle of Linux system
use. If you're a user of Microsoft Windows, you're accustomed
to a pattern of system use that forms a cycle:
The cycle of Linux system use is similar, even though you
perform the tasks somewhat differently.
Most Linux users boot their system from its hard
drive. Of course, if you made a boot diskette during system
installation, you can use it to boot your system.
First, you must prepare your system for booting. If your
system is running, you must shut it down by following the
proper procedure for shutting down the operating system
that's active. For example, if you're running Microsoft
Windows, click Start 
Shut Down and select the Shut
Down option in the Shut Down dialog box. Press OK to begin
the system shutdown. After a few seconds, Windows displays a
screen telling you that it's safe to turn off power to your
system. Turn off the power or, if your system automatically
powers down, wait a few seconds until the system powers
itself down.
Next, you must set your system to boot from the desired
device. To boot your system from its hard drive, remove any
floppy diskette from your system's floppy drive. To boot
your system from a floppy diskette, insert your Linux boot
diskette into your system's floppy drive.
Now, you're ready to boot your system. Switch your
system on (or press your system's reset button, if your
system is powered on) and watch as it performs its self
test. Shortly thereafter, you should see a
boot: prompt on the system's monitor. If
you like, you can list the available boot configurations
stored on the boot device by pressing
Tab. To boot the
system, type the name of the desired configuration and press
Enter, or simply press
Enter to boot using the default
configuration.
Once it loads, Linux begins probing your system and its
devices, printing status information on your system's
monitor. This status information is helpful if your system
fails to boot properly, because it discloses the point in
the boot process where the problem occurred.
When Linux has completed its boot process, your system's
monitor will display a login prompt similar to this:
Debian GNU/Linux 2.1 desktop tty1
desktop login:
Before you can use the system, you must identify
yourself by logging in. The install program created a
special user named
root; by identifying
yourself as the
root user, you can gain
access to the system. Normally, you use the
root userid only when performing system
administration tasks, because the
root
user has special capabilities that other users
lack.
To log on, type
root and press
Enter. The system prompts you
for the password associated with the
root
userid. Type the password you established during the
installation process and press
Enter. To prevent anyone nearby from
learning your password, Linux does not display it as you
type. If you suspect you've typed it incorrectly, simply
press
Enter and start over;
or press
Backspace once (or
more) for each character you've entered and then re-enter
it. If you type the userid or password incorrectly, Linux
displays the message "login incorrect" and prompts you to
try again.
Like other members of the Unix family, the Linux
operating system is case sensitive. Be sure to type the
userid
root just as it appears, using all
lowercase characters. Similarly, you must type the password
exactly as you entered it in the Root Password
dialog box during system installation.
Also, some Linux programs require you to type Ctrl-BACKSPACE, rather than BACKSPACE. If you press BACKSPACE and see
^H echoed to the console, try pressing Ctrl-BACKSPACE instead.
When you've successfully logged in, you'll see a command
prompt that looks something like this:
root@desktop:/root#
This prompt tells you that the Linux
bash shell is ready to accept your
commands.
The component of Linux that interprets and executes
commands is called the
shell. Linux
supports a variety of different shells, but the most popular
is the
bash shell. This chapter presents
the basics of using the
bash shell;
you'll learn more about the shell in Chapter 13,
Conquering the BASH Shell.
The Linux
bash shell presents the
user with a command-line interface (CLI). CLIs are familiar
to Windows users who have worked in the MS-DOS Prompt window, and
indeed the Microsoft Windows MS-DOS Prompt window is a kind
of command-line shell for Windows. The Linux
bash shell works much like the MS-DOS
Prompt window. You type text commands and the system
responds by displaying text replies. As your first Linux
command, type
w and press
Enter. Your
screen should look something like this:
root@desktop:/root#
w
11:12am up 6 min, 1 user, load average: 0.00, 0.08, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty1 11:13am 0.00s 0.20s 0.11s -bash
The
w command tells Linux to display
the system status and a list of all system users. In the
example, the output of the command tells you that it's now
11:12 a.m., that the system has been up for 6 minutes, and
that only one user -
root - is
currently logged in. Notice that the command output is very
terse, packing much information into a few lines. Such
output is typical of Linux commands. At first, you may find
Linux output cryptic and difficult to read, but over time
you'll grow to appreciate the efficiency with which Linux
communicates information.
Linux provides many commands besides the
w command; so many that you may despair
of learning and recalling them. Actually, the number of
commands you'll use regularly is fairly small. Soon, these
will become second nature to you.
Now try a second command, the
date
command:
root@desktop:/root#
date
Tue Feb 23 11:15:20 PST 1999
The
date command displays the current
date and time.
If you find working with MS-DOS distasteful or
intimidating, you may not immediately enjoy working with
the Linux command line. However, give yourself some time
to adjust. The Linux command line has several features
that make it easier to use, and more powerful, than
MS-DOS. If, after working with the Linux command line for
several days, you don't find yourself at home, don't
despair. Linux provides a graphical user interface in
addition to its command-line interface. You'll learn about
the graphical user interface in Chapter 6,
Using the X Window System.
Sometimes you may type a command incorrectly, causing Linux to display an error message. For example, suppose you
typed
dat instead of
date:
root@desktop:/root#
dat
bash: dat: command not found
In such a case, carefully check the spelling of the
command and try again. If you notice an error before
pressing
Enter, you can use
the
Backspace key to return
to the point of the error and then type the correct
characters.
Just as a web browser keeps track of recently visited
sites, Linux's BASH shell keeps track of recently
issued commands. This list is called the history list, and
you can scroll back through it using the Up arrow key, or
back down using the Down arrow key, just as you would with
the Back and Forward buttons on a web browser. In fact, the
history list provides several powerful ways to remember and
reuse frequently issued commands, as we'll see in
Chapter 13.
The Up and Down arrow keys let you scroll through a list of
commands recently issued. This feature is handy when you
want to repeat a command. Simply use the Up arrow key to find the
command and press
Enter to re-execute it. You can also use
this feature when you want to issue a command similar to one
you recently issued. Use the Up arrow key to find the original
command. Then, use the Left and Right arrow keys to position the
cursor and make whatever changes to the command you
like. Finally, press
Enter to execute the command.
In Microsoft Windows, you can have several MS-DOS Prompt
windows simultaneously active. Although the
bash shell doesn't have a graphical user
interface, you can nevertheless work with several instances
of the shell, by using Linux virtual consoles. Linux
provides six virtual consoles; you can use special
keystrokes to switch between them. The keystroke
Alt-F
n, where
n is the number of a virtual console
(1-6), causes Linux to display virtual console
n. For example, you can display virtual
console 2 by typing
Alt-F2. You can view only a single
console at a time, but you can switch rapidly between
consoles by using the appropriate keystroke.
Virtual consoles are handy when you've started a
time-consuming task and want to be able to perform an
unrelated task while the original task is working. You'll
also find them useful after you've established several
userids on your system, because you can log on as one userid
on one virtual console while you're logged on as another
userid on a different console.
Virtual consoles have a screen saver feature like that
found on Microsoft Windows. If a virtual console is inactive
for an extended period, Linux blanks the monitor screen. To
restore the screen without disturbing its contents,
press the
Shift key.
When you're done using a virtual console, you should log
out by typing the command
exit and
pressing
Enter. When you log out, the system frees memory
and other resources that were allocated when you logged in,
making those resources available to other users.
When the system logs you out, it immediately displays a
login prompt. If you change your mind and want to
access the system, you can login simply by supplying your
userid and password.
You shouldn't turn off power to a computer while it's
running Linux; instead, you should shut down the operating
system and then turn off power. To shut down a Linux system,
you use the
shutdown command, which
resides in a directory named
/sbin:
root@desktop:/root#
/sbin/shutdown -h now
Don't type the prompt, which automatically appears on
the command line. Only the
root user can
issue the
shutdown command. If you want
to restart a Linux system, you can use an alternative form
of the
shutdown command:
root@desktop:/root#
/sbin/shutdown -r now
Or, even more conveniently, you can use the familiar
MS-DOS "three-finger salute":
Ctrl-Alt-Del, which simply issues a
shutdown command on your behalf.
When you shut down a system, Linux automatically logs
off all users, terminates all running programs, and closes
all open files. Before shutting down a system, you should
check each virtual console to determine if an important
operation is in progress. If so, you should delay shutting
the system down until the operation completes.
